1. Field of the Invention
The present invention relates to a toxic substance-detecting device which detects toxic substances in water by use of a microorganism sensor to ascertain the safety of affluents flowing into sewage-treating processes, environmental waters such as rivers, and waters flowing into water purification plants. The present invention also relates to a water quality-monitoring system employing a detecting device.
2. Discussion of the Related Art
If toxic substances, such as phenols, cyanogen, arsenic, and heavy metals, accidentally come into contact with wastewaters discharged from factories and the contaminated wastewaters flow into sewage works, the activated-sludge microorganisms (hereinafter referred to as activated sludges) which play a major role in the sewage-treating processes can be severely damaged.
High concentrations of such toxic substances lower the activity of the activated sludges which greatly increases recovery time. If the inflow of wastewater contaminated by a toxic substance can be detected beforehand, water contamination from toxic substances can be greatly diminished by conducting a neutralization treatment in the primary sedimentation tank before the activated sludge treatment. For this reason, a device is desired that can detect the presence of a toxic substance in wastewater before the inflow of wastewater or at the time the wastewater has just flowed into sewage works.
Although the discharge of toxic substances may be controlled by regulating the concentrations of specific chemical substances in wastewaters, measuring techniques which have been developed heretofore cannot determine the concentrations of all toxic substances and are insufficient in maintaining the quality of all public waters. To measure the concentrations of toxic substances, there are techniques such as colorimetry and ion electrode method for cyanogen, atomic-absorption spectroscopy for heavy metals and GC-MS method for agricultural chemicals. However, it is technically and economically difficult to conduct continuous chemical examinations for determining the concentrations of a variety of toxic substances.
In the case of tap water, however, there has been proposed a method to control the quality of inflowing waters by means of a biological toxicity test. In this method, 10 to 20 fish are released in a pool filled with the water to be examined and the presence or absence of a toxic substance or the degree of toxicity is judged from the reactions and death rate of the fish after a fixed time period. However, this method, in which the water quality is judged based on the behavior and health condition of each fish, is defective in that the method is ambiguous and not suited for quantitative analysis, and factors which may affect the behavior of the fish is not taken into account. Therefore, the success of this method greatly depends on the experience of the operator and detection of toxic substances in early stages is difficult.
The conventional methods described above have the following practical problems: (1) clear results require a long period of time which prevents prompt treatment of the contamination; and (2) only high levels of concentration are detectable, i.e. toxic substances present at low concentrations cannot be detected.